The subject matter disclosed herein relates to ceramic heating devices.
Modern day aircraft utilize a number of sensors to aid in flight, including air speed sensors, angle of attack sensors, and bulbous wing tip sensors. These sensors are critical to provide flight information to the pilot. A number of these sensors are located externally on the aircraft surface and therefore are subjected to abrasive conditions and extreme temperatures. One problem with external sensors is their susceptibility to icing, which can prevent the sensor from providing accurate data or any data at all.
Wire wound heating devices are used to prevent icing of surfaces of external aircraft sensors by placing the heating devices in or on the sensors. Since the heat produced by the wire wound heating device is directly related to the resistance of the wire and the typically constant voltage applied, the wire wound heating device has a constant current output designed to provide sufficient heat to prevent icing in conditions during flight. But when the icing conditions are not present, the wire wound heating device can reach extremely high temperatures, reducing the reliability and life span of the heating device and jeopardizing the performance of the sensor that is to be protected by the heating device. For example, a wire wound heating device may reach temperatures as high as 300° C. when an aircraft is taxiing on the ground and there are no icing conditions. This results in the wire wound heating device experiencing a much higher temperature when the aircraft is grounded compared to when in flight, subjecting the heating device to severe thermal cycling that can increase the risk of failure.
Ceramic heating devices have also been used to prevent icing of surfaces of external aircraft sensors. Ceramic heating devices are conventionally fabricated using pressing operations to produce flat, planar heating devices which can be used to make shapes that are basically two-dimensional forms. U.S. Patent Application Publication No. US2010/0116806 A1 relates to utilizing ceramic heating devices within a pitot tube air speed sensor design using flat-faced, pellet heating devices in a radial arrangement along the surface of the body of the sensor. Consequently, the array of two-dimensional ceramic heating devices is not continuous or closely matched to the internal surface profile of the surface of the sensor. The multi-component design adds complexity and cost while reducing the efficiency of heat transfer to the surface of the sensor.
The discussion above is merely provided for general background information and is not intended to be used as an aid in determining the scope of the claimed subject matter.